Field of the Invention (Technical Field)
The present invention is in the field of a composition for forming a bio-compatible membrane applicable to building material, such as concrete, cement, etc., to a method of applying said composition for forming a bio-compatible membrane, a bio-compatible membrane, use of said membrane for various purposes, and to building material comprising said membrane.
Background of the Invention
Concrete is a composite construction material composed primarily of aggregate, cement and water, with mortar being similar thereto, however using finer aggregates. There are many formulations that have varied properties. The aggregate is generally a coarse gravel or crushed rocks such as limestone, or granite, along with a fine aggregate such as sand. The cement, commonly Portland cement, and other cementing materials such as fly ash, blast furnace slag cement, ground calcium carbonate, etc. serve as a part of binder for the aggregate. Typically further additives are present.
Various chemical admixtures can be added to achieve varied properties. Water is thereafter mixed with this dry or moist composite which enables it to be shaped (typically poured) and then solidified and hardened into rock-hard strength through a mineralogical transformation known as hydration and/or pozzolanic reaction. Also particle size and polarity of materials play a role in the performance of concrete. Concrete may be reinforced with materials that are strong in tension (often steel).
Admixtures are ingredients other than water, fine aggregates, (hydraulic) cement, and fibers that are added to the concrete batch immediately before or during mixing, in order to change certain characteristics of the concrete, when set.
For concrete production the various ingredients mentioned above are mixed. It is noted that concrete production is time-sensitive. Once the ingredients are mixed, the concrete must be put in place before it hardens, such as by casting. Then, quite critical as well, care must be taken to properly cure concrete, e.g. to achieve a required strength and hardness. It is noted that cement requires a moist, controlled environment to gain strength and harden fully. Such is often difficult to provide and to maintain. The cement paste hardens over a relatively long period of time, initially setting and becoming rigid though very weak and gaining in strength in the weeks following. It is noted that hydration and hardening of concrete initially, i.e. during the first three days, is considered critical. Abnormally fast drying and/or shrinkage are unwanted. It is considered of importance that concrete is kept sealed during the initial curing process. Such may be achieved by spraying or ponding the concrete surface with water, thereby protecting the concrete mass from harmful effects of ambient conditions. Additional common curing methods include wet burlap and/or plastic or paper sheeting covering the fresh concrete, or by spraying on a water-impermeable temporary curing membrane. In a prior art example a minimum thickness of e.g. 0.01 mm is required to ensure adequate strength in the (membrane) sheet (see e.g. ASTM C 171). Concrete should therein be covered with a membrane, either of plastic or of a chemical compound that will likely seal off the pores and retard the evaporation of water from concrete. After use such a sheet is typically removed. It is observed such a sheet does typically not fully cover concrete. A sheet may also be somewhat difficult to apply, especially when concrete is curved it is difficult to access, such as in high buildings and hidden areas, it may be of temporary nature, it can not be fully integrated with an underlying material, permeability may be difficult to adapt, toxic chemicals and solvents may be used, diffusion of membrane or constituents into concrete may take place, they may be sensitive with respect to time of application, typically they are non-degradable, and they may not be environmentally friendly.
In the context of the present invention a (semi)permeable membrane relates to a partially permeable membrane or a differentially permeable membrane. Such a membrane allows certain molecules or ions to pass through it by diffusion, such as gaseous species. It is noted that a rate of passage depends on various parameters, such as pressure difference, concentration difference, and temperature difference between circumstances on either side of a membrane, and permeability of the membrane to a given species, which permeability depends on solute or species size, solubility, chemistry, etc.
Once fully set, concrete may be prone to deterioration, such as by environmental influences. Therefore, after setting also protection from deterioration is preferred.
Incidentally various aqueous like compositions are known, comprising membrane forming constituents.
U.S. Pat. No. 4,316,833 (A) recites a liquid system containing no water to form an underground waterproof coating material containing a high concentration (70%+) of bentonite (sodium montmorilionite) which is non-hydrated, non-emulsifiable, unexpanded, non-jelled, non-thixotropic but is sufficiently liquid to be applied to a wood, metal or concrete substrate by a caulking gun, trowel or spray method. It can be used over a wide range of temperatures and can be applied to damp surfaces. The invention relates to a bentonite based composition for coating walls or sealing joints in concrete, and sealing around pipe openings and the like in building construction. The composition can be used for any type of waterproofing or water stop application if desired. Water cannot be used as or contained in the liquefier because it will destroy the properties of the system by hydrating the bentonite. The system may comprise beads, which beads may be coated with Ca-alginate. From the above it is clear that the system has no capability to form a membrane; it is solely intended to swell. Application is therefore inside cracks and the like, in order to seal.
CN101502868 (A) recites a centrifugal casting radiant tube coating and a preparation method thereof, the coating comprises the ingredients (mass percent) of: amongst others 25-30% of diatomite of, 5-10% of zircon powder, 4.5-5.0% of sodium bentonite, 2.0-2.5% of polyvinyl alcohol, 0.8-1.0% of sodium alginate, 3.5-4.0% of silica sol, and 46.82-49.95% of water, wherein, the mass percent of the diatomite and the zircon powder is not less than 35% and not more than 37%, the mass percent of titanium powder and iron powder is not less than 2.7% and not more than 2.9%, and the mass percent of the sodium bentonite plus the polyvinyl alcohol plus the sodium alginate is not less than 8.0% and not more than 8.2%. The coating is used for the centrifugal casting radiant tube after dry-blending, mixed grinding and sieving, uniformly distributed bulges (namely pitting surface) can be formed on the outer surface of the radiant tube to improve heat efficiency of the radiant tube. The coating also has excellent adhesive force, high temperature strength and crack resistance, thus reducing defects on the surface of the radiant tube and improving quality of complex tube.
The above two documents do not relate to an aqueous bio-compatible solution that can be applied on a surface.
Thus there is a need for improved membranes.
The present invention relates to a composition for forming such a membrane, use thereof, and material comprising said membrane, which overcomes one or more of the above disadvantages, without jeopardizing functionality and advantages.